Axle driving apparatus

ABSTRACT

An axle driving apparatus comprises: a common housing; a pair of coaxial axles disposed in the housing; a common input shaft for receiving power from a prime mover, the common input shaft being extended perpendicular to the axles in the housing and passed through a gap between the axles; and a pair of stepless transmissions sharing power from the common input shaft, and transmitting power to the respective axles. The pair of stepless transmissions are arranged in the housing symmetrically centered on an axis of the common input shaft. The axle driving apparatus further comprises: a PTO shaft disposed coaxially to the common input shaft; a clutch disposed in the housing and interposed between the common input shaft and the PTO shaft; and a brake which is applied simultaneously to disengagement of said clutch so as to prevent inertial rotation of said PTO shaft.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.10/644,753, filed Aug. 21, 2003, which is incorporated herein byreference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an axle driving apparatus having acommon housing enclosing a pair of hydrostatic transmissions(hereinafter referred to as “HSTs”) and a pair of axles individuallydriven by the respective HSTs.

2.Background of the Invention

Conventionally, as disclosed in Japanese Patent Laid Open Gazette Hei.7-323739, there is a well-known integrated hydrostatic transaxle(hereinafter referred to as an “IHT”) which is applicable for asnowblower. The IHT comprises a common housing, a pair of HSTs, each ofwhich is a combination of a hydraulic pump and a hydraulic motor, and apair of coaxial axles individually driven by the respective HSTs,wherein the HSTs and the axles are housed within the housing.

In the conventional IHT, in order to economically make a commonconstruction between the left and right drive trains from the respectiveHSTs to the respective axles, the pair of HSTs are disposed laterallysymmetrically (in the axial direction of the axles) so as to equalizelateral positions of the HSTs relative to the respective axles (in theaxial direction of the axles). However, the pair of HSTs are disposedlaterally symmetrically with respect to a vertical line, and thehydraulic pump and hydraulic motor of each HST are juxtaposed laterallyin order to vertically downsize the IHT. Consequently, two hydraulicpump and motor pairs are laterally aligned on the substantially samevertical level so that the conventional IHT including the housing isentirely elongated laterally in the axial direction of the axles.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an axle drivingapparatus including a common housing incorporating a pair of steplesstransmissions and a pair of coaxial axles individually driven by therespective transmissions, wherein the size of the axle driving apparatusin the axial direction of the axles is reduced, while the symmetry ofthe stepless transmissions in the axial direction of the axles ismaintained.

To achieve the object, an axle driving apparatus comprises: a housing; apair of coaxial axles disposed in the housing; a common input shaft forreceiving power from a prime mover; and a pair of stepless transmissionssharing power from the common input shaft, and transmitting power to therespective axles. The common input shaft is extended perpendicular tothe axles in the housing and passed through a gap between the axles. Thepair of stepless transmissions are arranged in the housing symmetricallycentered on an axis of the common input shaft.

Therefore, the stepless transmissions are diagonally arranged so as tooverlap when viewed perpendicularly to the axles so that the size of theaxle driving apparatus including the housing in the axial direction ofthe axles is reduced, while the symmetry of the stepless transmissionsin the axial direction of the axles is maintained. In other words, theequality of positions of the stepless transmissions relative to therespective axles in the axial direction of the drive axles is maintainedso that a pair of drive trains from the respective steplesstransmissions to the respective axles may share common parts and mayhave equal operational efficiency.

Each of the stepless transmissions may be an HST, which includesmutually fluidly connected hydraulic pump and motor. The hydraulic pumpsare drivingly connected to the common input shaft, and the hydraulicmotors are drivingly connected to the respective axles. Preferably, thehydraulic pump and motor are aligned along each of the axles in theaxial direction, whereby the size of the axle driving apparatusincluding the housing is reduced perpendicularly to the axles, while itsexpansion in the axial direction of the axles is restrained by theabove-mentioned symmetric arrangement of the HSTs centered on the axisof the common input shaft. Further, the common input shaft may bedisposed in parallel to rotary axes of the hydraulic pumps, therebysimplifying the driving connection between the input shaft and the HSTs.

Further, preferably, in each of the HSTs, the hydraulic pump and motorhave mutually perpendicular rotary axes. Therefore, even if thehydraulic pump has a rotary axis perpendicular to the axle availably forinputting power from an engine, the hydraulic motor has a rotary axisparallel to the axle so that the hydraulic motor may be drivinglyconnected to the corresponding axle using inexpensive parts such as spurgears.

Further, preferably, the axle driving apparatus further comprises: a PTOshaft disposed coaxially to the common input shaft; and a clutchdisposed in the housing and interposed between the input shaft and thePTO shaft. Therefore, no drive train, e.g., no gear train, is drivinglyinterposed between the common input shaft and the PTO shaft, therebyreducing the number of parts, costs, and the size of the axle drivingapparatus.

Further, preferably, the axle driving apparatus further comprises abrake which is applied simultaneously to disengagement of the clutch soas to prevent inertial rotation of the PTO shaft. Thus, the stationaryPTO shaft can be easily located to be drivingly connected to a workingattachment.

These, further and other objects, features and advantages will beapparent more fully from the following description.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a left side view of a snowblower equipped with an axle drivingapparatus according to a first embodiment of the present invention.

FIG. 2 is a front view of a mechanism for driving a traveling device anda snow-removing header in the snowblower.

FIG. 3 is a front view of the axle driving apparatus.

FIG. 4 is a sectional rear view of the axle driving apparatus.

FIG. 5 is a sectional plan view of the axle driving apparatus.

FIG. 6 is a sectional view in the direction of the arrows VI-VI of FIG.4.

FIG. 7 is a sectional view in the direction of the arrows VII-VII ofFIG. 4.

FIG. 8 is a side view of a riding lawn mower equipped with an axledriving apparatus according to a second embodiment of the presentinvention.

FIG. 9 is a sectional rear view of the axle driving apparatus accordingto the second embodiment.

FIG. 10 is a sectional side view of the axle driving apparatus accordingto the second embodiment.

DETAILED DESCRIPTION OF THE INVENTION

A snowblower having an axle driving apparatus of the present inventionwill now be described with particular reference to FIG. 1. Although asnowblower having the axle driving apparatus is described in thisembodiment, the axle driving apparatus of the present invention is alsoapplicable to small size vehicles, such as a lawn mower or a smallconstruction machine (including a road maintenance machine).

A pair of left and right handles 2 are extended upwardly backward fromthe rear ends of a main frame 1. A main clutch lever 50, left and rightspeed changing levers 3L and 3R, and an accelerator lever are disposedbetween the top portions of handles 2. An engine 4 is mounted on mainframe 1. A header 5 is disposed in front of main frame 1. Header 5comprises a blower case 6 and an auger case 7 which is disposed in frontof blower case 6. A plowing auger 8 having a lateral rotary shaft isarranged in the auger case 7. A gear box 9 is disposed on the lateralcenter of the rotary shaft of the plowing auger 8 so as to transferpower from engine 4 to the rotary shaft to thereby drive plowing auger8. A chute 10 for discharging snow projects upward from blower case 6.

As shown in FIGS. 1 and 2, a double output pulley 12 having two frontand rear output pulleys 12 a and 12 b is disposed on an output shaft 11of engine 4. A pulley 14 incorporating a clutch is disposed on a blowershaft 13 extended lengthwise in blower case 6. Pulley 14 and outputpulley 12 a are bound by a belt 15 so as to drive blower 16 and plowingauger 8 with power of engine 4.

Output pulley 12 b and an input pulley 17 of a later-discussed axledriving apparatus are bound by a belt 18 so as to transmit power fromengine 4 to a pair of HSTs in a housing 100 of the axle drivingapparatus. In the axle driving apparatus, the pair of HSTs individuallydrives respective drive axles 35L and 35R, shown in FIG. 2, at variousspeeds either forward or rearward.

A pair of chain casings 36 are disposed on left and right sides ofhousing 100 of the axle driving apparatus, respectively. Each of chaincasings 36 contains a chain transmission interposed between each ofdrive axles 35L and 35R and each of final axles 20L and 20R (representedas “20” in FIG. 1). Left and right drive sprockets 21 are disposed onouter ends of respective final axles 20L and 20R. Left and rightfollower sprockets 22 are journalled by a rear portion of a track framefixed to the bottom portion of main frame 1. Left and right crawlers 23are wound around left sprockets 22 and 23, so as to constitute acrawler-type traveling device.

Referring to FIGS. 3 to 7, a mechanism in the axle driving apparatus ofthe present invention will now be described. As shown in FIG. 6, housing100 of the axle driving apparatus comprises a front housing part 30, amiddle housing part 31, and a rear housing part 32. Three housing parts30, 31 and 32 are mutually joined through respective joint surfaceswhich are vertically and laterally expanded. As shown in FIG. 4, a pairof left and right motor shafts 33, a pair of left and right countershafts 34 and the pair of drive axles 35L and 35R are laterally extendedin parallel in housing 100. On the joint surface between middle housingpart 31 and rear housing part 32 are disposed axes of motor shafts 33and counter shafts 34, and middle and rear housing parts 31 and 32sandwich respective bearings for motor shafts 33 and counter shafts 34.Drive axles 35L and 35R are mutually coaxially arranged in front of thejoint surface between middle housing 31 and rear housing 32, andjournalled by left and right side ends of middle housing 31,respectively.

As shown in FIGS. 4 to 6, in a first chamber formed by middle housingpart 31 and rear housing part 32, the pair of HSTs for transmittingpower to the respective drive axles 35L and 35R are disposedsymmetrically centered on a point on the extended longitudinal axis ofdrive axles 35L and 35R in a gap between drive axles 35L and 35R. Inother words, both the HSTs are arranged diagonally, i.e., laterally andvertically symmetrically so that they are laterally distributed and alsovertically distributed oppositely with respect to drive axles 35L and35R. In this embodiment, as shown in FIG. 4, the left HST is disposedabove left drive axle 35L, and the right HST below right drive axle 35R,however, the left and right HSTs may be interchanged in verticallocation. Each of the HSTs is constituted by fluidly connecting ahydraulic pump 41 to a hydraulic motor 43 through a center section 40.

According to the arrangement of the axle driving apparatus in theillustrated snowblower, input shaft 39 is disposed horizontally so as tolocate the right HST under right drive axle 35R and to expand theportion of housing 100 for the right HST downward. Corresponding to thissituation, the pair of chain casings 36 are provided for ensuringsufficient road clearance. If the axle driving apparatus is loaded on alawn mower having a vertical engine, input shaft 39 is disposedvertically so as to reduce the downward expansion of housing 100.Therefore, it is unnecessary to provide chain casings 36 for ensuringroad clearance, and drive axles 35L and 35R may be directly connected atouter ends thereof to respective tires.

As shown in FIG. 6, front housing part 30 and middle housing part 31constitute a second chamber for housing transmission gears 24, 25 and26. Pump shafts 45 of the pair of hydraulic pumps 41 project forward,i.e., perpendicularly to drive axles 35L and 35R and motor shafts 33,into the second chamber. In the second chamber, one of pump shafts 45 isprovided on the front end thereof with gear 26. The other pump shaft 45,provided thereon with gear 24 in the second chamber, projects forwardfrom front housing part 30, i.e., from the front end of housing 100, soas to serve as input shaft 39 of both the HSTs. Alternatively, inputshaft 39 may be a member separated from pump shaft 45, or a gear shaftof gear 25 between gears 24 and 26 fixed on respective pump shafts 45may be projected forward from housing 100 so as to serve as input shaft39. Front and middle housing parts 30 and 31 journals a counter shaft 25a, which is extended lengthwise, i.e., in parallel to pump shafts 45,and is fixedly provided thereon with gear 25. Gears 24 and 26 mesh witheach other through gear 25 so that both pump shafts 45 aresimultaneously driven in the same direction by rotary force inputted toinput shaft 39.

The first and second chambers of housing 100 are filled with hydraulicoil for the HSTs which is also used as lubricating oil, so as to form anoil sump. As shown in FIG. 6, a pipe joint 27 is disposed on an upperportion of housing 100 (rear housing part 32). A piping 28 such as arubber hose is extended from pipe joint 27 and connected to a reservoirtank 29, which is disposed outside housing 100 as shown in FIG. 1, so asto fluidly connect the oil sump to reservoir tank 29, so that reservoirtank 29 absorbs the excessive volume of hydraulic oil expanded by heatof the HSTs in operation.

In order to realize the above-mentioned symmetrical arrangement of HSTscentered on point P in the first chamber, as shown in FIG. 4, the pairof center sections 40 are disposed laterally and verticallysymmetrically centered on point P on the extended axis of drive axles35L and 35R in the gap between drive axles 35L and 35R. Each of centersections 40 is L-like shaped when viewed in plan, as shown in FIG. 5. Ona laterally vertical front surface of center section 40 is formed a pumpmounting surface 42 onto which hydraulic pump 41 is mounted. On alongitudinally vertical side surface of center section 40 is formed amotor mounting surface 44 onto which hydraulic motor 43 is mounted. Pumpmounting surfaces 42 of the pair of center sections 40 are arranged soas to coincide with the joint surface between middle housing part 31 andrear housing part 32, thereby concentrating both the HSTs to theapproximate middle of housing 100 in the fore-and-aft direction.

Description will now be given on each of variable displacement hydraulicpumps 41 in accordance with FIGS. 4 to 6. Each of pump shafts 45 isrotatably supported within center section 40, and extended forward fromcenter section 40 through the center of pump mounting surface 42. Acylinder block 46 having a plurality of cylinder bores is rotatably andslidably fitted to each pump mounting surface 42. Pistons 47 withcooperating and biasing springs are reciprocally inserted into therespective cylinder bores of cylinder block 46. A pair of movable swashplates 48 are slidably rotatably fitted to a front wall of middlehousing part 31. A thrust bearing of each movable swash plate 48 abutsagainst heads of pistons 47 of each cylinder block 46. Each of pumpshafts 45 axially penetrates cylinder block 46 and is not relativelyrotatably fitted to cylinder block 45. Further, each pump shaft 45freely rotatably penetrates movable swash plate 48 while allowing forthe rotation of movable swash plate 48. Consequently, both pump shafts45 rotatably penetrate the front wall of middle housing part 31 throughrespective bearings so as to be inserted into the second chamber asmentioned above.

Each of movable swash plates 48 is individually angularly adjustablewith respect to the rotary axis of cylinder block 46 so as to vary theamount and direction of hydraulic oil discharged from each of hydraulicpumps 41. Movable swash plate 48 has an arcuate convex surface thatcooperates with each of arcuate concave surfaces formed in the frontwall of middle housing part 31. Movable swash plate 48 tilted for itsangular adjustment is slidably guided along the concave surface ofmiddle housing part 31.

As shown in FIG. 4, a pair of control shafts 51 for angularly adjustingrespective movable swash plates 48 are disposed in parallel to driveaxles 35L and 35R and arranged laterally and vertically symmetricallycentered on point P between drive axles 35L and 35R. Control shafts 51are journalled by middle housing part 31. One control shaft 51 isdisposed at the left end wall of middle housing part 31 above left driveaxle 35L, and the other control shaft 51 is disposed at the right endwall of middle housing part 31 below right drive axle 35R. A pair ofcontrol levers 52 are fixed on outer ends of respective control shafts51 outside housing 100. In housing 100, a pair of swing arms 53 arefixed onto inner ends of respective control shafts 51 and engage at tipsthereof into side grooves of respective movable swash plates 48. Wheneither left or right control lever 52 is rotated either forward orrearward, control shaft 51 and swing arm 53 integrated with rotatedcontrol lever 52 are rotated so as to tilt corresponding movable swashplate 48 and change the output of corresponding hydraulic pump 41.

Description will now be given of each of hydraulic motors 43 inaccordance with FIGS. 4, 5 and 6. A cylinder block 57 of each hydraulicmotor 43 is slidably rotatably fitted onto motor mounting surface 44 ofeach center section 40. A plurality of pistons 58 are reciprocallyinserted through biasing springs into a plurality of cylinder bores ofcylinder block 57. Heads of pistons 58 abut against a fixed swash plate59 immovably sandwiched between middle housing part 31 and rear housingpart 32. Each of motor shafts 33 is axially inserted into cylinder block57 and not relatively rotatably fitted thereto. Each of motor shafts 33is extended laterally horizontally, i.e., parallel to each of driveaxles 35L and 35R from cylinder block 57 and penetrates correspondingswash plate 59 and a corresponding bearing sandwiched between middle andrear housing parts 31 and 32.

Description will now be given of each of center sections 40 inaccordance with FIGS. 4 to 6. As shown in FIG. 4, center sections 40 arefixed to rear housing part 32 with bolts. Alternatively, center sections40 may be fastened to middle housing part 31. Center section 40 isdesirably removable from housing 100.

On pump mounting surface 42 of each center section 40 are disposed apair of arcuate ports around pump shaft 45 in fluid communication withthe cylinder bores in cylinder block 46 of hydraulic pump 41. On motormounting surface 44 of each center section 40 are disposed a pair ofarcuate ports around motor shaft 33 in fluid communication with thecylinder bores in cylinder block 57 of hydraulic motor 43. As shown inFIG. 6, within each center section 40, an upper oil passage 40 a and alower oil passage 40 b are bored so as to connect the respective arcuateports on pump mounting surface 42 to the respective arcuate ports onmotor mounting surface 44, thereby constituting a closed hydrauliccircuit for mutually fluidly connecting hydraulic pump 41 and motor 43.

Check valves 61 and 62 are fitted forward into each center section 40 soas to be connected to respective oil passages 40 a and 40 b. Ahorizontally cylindrical oil filter 63 is interposed between rearhousing part 32 and the rear end surface of each center section 40 so asto cover check valves 61 and 62. Therefore, hydraulic oil in housing 100is filtrated by each oil filter 63 and supplied into oil passage 40 athrough check valve 61, or into oil passage 40 b through check valve 62.

As shown in FIGS. 5 and 6, a pair of oil release members 64 are disposedbehind respective center sections 40 and supported by the rear wall ofrear housing part 32. When the snowblower with engine 4 shut down ishauled, each of oil relief members 64 is manually operated from theoutside of housing 100 so as to forcibly open check valves 61 and 62 andrelease oil from oil passages 40 a and 40 b to the oil sump in housing100. Due to this oil pressure relief, in each of the HSTs, hydraulicmotor 43 interlocking with corresponding axle 35L or 35R and 20 becomesfree from the fluid connection with hydraulic pump 41, so thatcorresponding drive sprocket 21 is freely rotated according to thehauling of the snowblower and hydraulic pump 41 is prevented fromreceiving back flow of hydraulic oil caused by rotation of hydraulicmotor 43, thereby protecting the HST and engine 4.

Description will now be given of the gear train from each motor shaft 33to each of drive axles 35L and 35R in accordance with FIGS. 4, 5 and 7.As shown in FIG. 4, each of counter shafts 34 parallel to motor shaft 33and drive axle 35L or 35R is disposed between motor shaft 33 andcorresponding drive axle 35L or 35R in rear (front) view as shown inFIG. 4, and aligned with motor shaft 33 in a vertical row in side viewas shown in FIG. 7. Each of motor shafts 33 projects from theabove-mentioned bearing and is sandwiched between middle and rearhousing parts 31 and 32 opposite to fixed swash plate 59. Thisprojecting portion of motor shaft 33 is peripherally formed into a gear65, which meshes with a diametrically larger gear 67 fixed on countershaft 34. Counter shaft 34 is peripherally formed with a gear 68, whichmeshes with a diametrically larger gear 69 fixed on each of drive axles35L and 35R. In this way, between motor shaft 33 and corresponding driveaxle 35L or 35R is constructed a reduction gear train including gears65, 67, 68 and 69.

Description will now be given on a pair of locking mechanisms providedfor the respective drive trains for the drive axles 35L and 35R so as toconstitute a parking brake system of the snowblower, in accordance withFIGS. 3 to 5 and 7. More specifically, each of the locking mechanismsdirectly locks corresponding motor shaft 33 so as to lock thecorresponding drive train from motor shaft 33 to crawler 23. As shown inFIGS. 4 and 5, each motor shaft 33 is fixedly provided on the tipthereof with a locking disk 66. Each locking disk 66 is provided on theperipheral edge thereof with a plurality of (in this embodiment, four)detent notches 66 a, as shown in FIG. 7. On the other hand, as shown inFIGS. 5 and 7, a pair of locking shafts 71 are longitudinally slidablysupported by middle housing part 31 through respective bushes 75 inperpendicular to respective motor shafts 33. The rear end of eachlocking shaft 71, when sliding rearward, enters any of detent notches 66a of each locking disk 66.

Locking shafts 71 projects outwardly forward from housing 100 (middlehousing part 31) so as to be diametrically penetrated by an engaging pin72. A pair of locking levers 74 are pivotally supported at theintermediate portions thereof by front end portions of middle housingpart 31 through respective pivotal pins 73. Each engaging pin 72 ispassed through a notch 74 a formed at the bottom end of each lockinglever 74 so as to pivotally connect locking lever 74 to locking shaft71. By forwardly rotating the top end of each locking lever 74, thebottom end of locking lever 74 below pivotal pin 73 is rotated rearwardso that locking shaft 71 slides rearward and enters one of detentnotches 66 a, thereby locking motor shaft 33 through locking disk 66.Therefore, the corresponding left or right drive system from motor shaft33 to crawler 23 is kept stationary.

As shown in FIG. 3, the pair of locking levers 74 are arranged in aspace in front part of middle housing part 31 on upper left side andlower right side of front housing part 30 containing transmission gears24, 25 and 26, thereby being prevented from interfering with anotherlever or link. Locking levers 74 are connected to each other through alink (not shown) and to a single parking brake lever (not shown). Bymanipulating the parking lever, both of locking levers 74 are movedthereby locking the left and right drive systems simultaneously.

As shown in FIG. 2, the left traveling drive system from left drive axle35L and left crawler 23 through left chain casing 36 and the righttraveling drive system from right drive axle 35R and right crawler 23through right chain casing 36 are laterally symmetric with housing 100therebetween. In housing 100, the left drive train from the left HST toleft drive axle 35L and the right drive train from the right drive trainto right drive axle 35R are symmetric centered on point P between driveaxles 35L and 35R on the axis thereof so that, as understood from FIG.4, the HST for left drive axle 35L and the HST for right drive axle 35Roverlap laterally when viewed in plan. Accordingly, the whole of axledriving apparatus including housing 100 is narrowed laterally.

For the snowblower shown in FIG. 1, the described axle driving apparatusis applied in the state that input shaft 39 projects forward, i.e., theleft and right HSTs are vertically distributed with drive axles 35L and35R therebetween. Alternatively, when the axle driving apparatus is usedfor a lawn mower having a vertical crankshaft engine, it may be arrangedso as to orient input shaft 39 vertically. In this case, the left andright HSTs come to be distributed in front and rear of drive axles 35Land 35R.

Further, the axle driving apparatus may be applied for constituting awheel type traveling device by directly attaching grounding wheels ontorespective drive axles 35L and 35R, as well as the crawler travelingdevice as shown in FIGS. 1 and 2.

An alternative axle driving apparatus 101 will be described withreference to FIGS. 8 to 10. Axle driving apparatus 101 has a PTO shaft127 and an input shaft 125 which are coaxially oppositely extendedforward and rearward from a housing of axle driving apparatus 101.

FIG. 8 illustrates a riding lawn mower 200 serving as an example of aworking vehicle equipped with axle driving apparatus 101. Riding lawnmower 200 has a chassis 201. A carrier 208 is (or carriers 208 are)supported on a front end portion of chassis 201. Axle driving apparatus101 is disposed at a longitudinal middle portion of riding lawn mower200 between left and right side frame portions of chassis 201. Left andright drive axles 35L and 35R project leftward and rightward from thehousing of axle driving apparatus 101, and penetrate the left and rightside frame portions of chassis 201 so as to be connected at distal endsthereof to respective left and right drive wheels 210.

The housing of axle driving apparatus 101 is constituted by mutuallyjoined front, middle and rear housing parts 32, 31 and 30, similar tothe housing of axle driving apparatus 100. To fix the housing to chassis201, as shown in FIGS. 8 and 9, middle housing part 31 is integrallyformed with left and right extended boss portions 31 a supportingrespective drive axles 35L and 35R, and outer ends of boss portions 31 aare fastened to the left and right side frame portions of chassis 201.As shown in FIG. 9, vertical penetrating bolt holes 31 b are formed inthe outer ends of boss portions 31 a so as to be used for fastening theouter ends of boss portions 31 a to the left and right side frameportions of chassis 201 with bolts.

As shown in FIG. 8, riding lawn mower 200 has a body cover 207 enclosingchassis 201. An operator's seat 203 is mounted on body cover 207 justabove axle driving apparatus 101. A pair of left and right speedchanging levers 202 (only one of them is illustrated in FIG. 8) areextended upright from body cover 207 just in front of seat 203, andoperatively connected through respective link rods 49 to respective leftand right control levers 52 pivoted on the housing of axle drivingapparatus 101. Control levers 52 interlock with respective movable swashplates 48 of hydraulic pumps 41 in the housing of axle driving apparatus101.

An engine 204 is supported by chassis 201 via vibratory isolatingsupporters 204 c behind axle driving apparatus 101. A radiator 205 isdisposed behind engine 204. Engine 204 has a front flywheel 204 aserving as an output terminal. A clutch shaft 130 projects forward fromflywheel 204 a, and is drivingly connected to flywheel 204 a via aclutch 204 b. Input shaft 125 of axle driving apparatus 101 projectsrearward from the housing of axle driving apparatus 101, and isdrivingly connected to clutch shaft 130 via a propeller shaft 129 anduniversal joints, thereby receiving power from engine 204.

A mower unit 209 containing a rotary mowing blade is suspended downwardfrom chassis 201 between carrier (carriers) 208 and axle drivingapparatus 101. PTO shaft 127 of axle driving apparatus 101 projectsforward from the housing of axle driving apparatus 101, and is drivinglyconnected to an input shaft 209 a of mower unit 209 via a propellershaft 128 and universal joints so as to drive the rotary mowing blade inmower unit 209.

Referring to FIGS. 9 and 10, similar to axle driving apparatus 100, axledriving apparatus 101 has HSTs disposed symmetrically centered on thecenter point in a gap between drive axles 35L and 35R in the housing.Each of the HSTs comprises mutually fluidly connected hydraulic pump 41and hydraulic motor 43, which are aligned in the axis direction of driveaxles 35L and 35R. In each of the HSTs, axial motor shaft 33 ofhydraulic motor 43 is disposed perpendicular to axial pump shaft 45 ofhydraulic pump 41, and disposed in parallel to each of drive axles 35Land 35R so as to be drivingly connected via the gear train tocorresponding drive axle 35L or 35R. In comparison with FIGS. 4 and 6,the same reference numerals designate the same members and portions,which have the same functions. Description of the same members andportions are omitted.

Input shaft 125 serves as a rotary shaft of gear 25 disposed betweengears 24 and 26 so as to distribute the input power between hydraulicpumps 41. In this regard, similar to lower hydraulic pump 41, upperhydraulic pump 41 also has pump shaft 45 which does not project outwardfrom the housing of axle driving apparatus 101. Gear 24 is fixed on pumpshaft 45 of upper hydraulic pump 41 and meshes with gear 25.

Input shaft 125 is extended forward in the housing and passed throughthe gap between proximal ends of drive axles 35L and 35R. Thus, the HSTsare symmetric centered on an axis of input shaft 125. A front centerportion of front housing part 32 projects forward so as to form a PTOhousing portion 32 a incorporating a PTO clutch-and-brake unit 126,which may be hydraulically or electromagnetically controlled. A frontend of input shaft 125 enters PTO housing portion 32 a, and is connectedto PTO clutch-and-brake unit 126. PTO shaft 127 projecting forward fromPTO housing portion 32 a is connected at a rear end thereof to PTOclutch-and-brake unit 126. PTO clutch-and-brake unit 126 has a clutchwhich is disengaged to isolate PTO shaft 127 from the rotary force ofinput shaft 125. PTO clutch-and-brake unit 126 has a brake which isapplied simultaneously to the disengagement of the clutch, therebypreventing inertial rotation of PTO shaft 127.

Although the present invention has been described in its preferred formwith a certain degree of particularity, it is understood that thepresent disclosure of the preferred form has been changed in the detailsof construction and the combination and arrangement of parts may beresorted to without departing from the spirit and the scope of theinvention as hereinafter claimed.

1. An axle driving apparatus, comprising: a housing; a pair of coaxialaxles disposed in said housing; a common input shaft for receiving powerfrom a prime mover, said common input shaft being extended perpendicularto said axles in said housing and passed through a gap between saidaxles; and a pair of stepless transmissions sharing power from saidcommon input shaft, and transmitting power to said respective axles,wherein said pair of stepless transmissions are arranged in said housingsymmetrically centered on an axis of said common input shaft.
 2. Theaxle driving apparatus as set forth in claim 1, further comprising: aPTO shaft disposed coaxially to said common input shaft; and a clutchdisposed in said housing and interposed between said common input shaftand said PTO shaft.
 3. The axle driving apparatus as set forth in claim2, further comprising: a brake which is applied simultaneously todisengagement of said clutch so as to prevent inertial rotation of saidPTO shaft.
 4. An axle driving apparatus, comprising: a housing; a pairof coaxial axles disposed in said housing; a common input shaft forreceiving power from a prime mover, said common input shaft beingextended perpendicular to said axles in said housing and passed througha gap between said axles; and a pair of hydrostatic transmissionsarranged in said housing symmetrically centered on an axis of saidcommon input shaft so as to share power from said common input shaft,wherein each of said hydrostatic transmissions includes mutually fluidlyconnected hydraulic pump and motor, said hydraulic pumps being drivinglyconnected to said common input shaft, and said hydraulic motors beingdrivingly connected to said respective axles, and wherein said hydraulicpump and said hydraulic motor in each of the hydrostatic transmissionsare aligned along said axle in the axis direction.
 5. The axle drivingapparatus as set forth in claim 4, further comprising: a PTO shaftdisposed coaxially to said common input shaft; and a clutch disposed insaid housing and interposed between said common input shaft and said PTOshaft.
 6. The axle driving apparatus as set forth in claim 5, furthercomprising: a brake which is applied simultaneously to disengagement ofsaid clutch so as to prevent inertial rotation of said PTO shaft.
 7. Anaxle driving apparatus, comprising: a housing; a pair of coaxial axlesdisposed in said housing; a common input shaft for receiving power froma prime mover, said common input shaft being extended perpendicular tosaid axles in said housing and passed through a gap between said axles;and a pair of hydrostatic transmissions arranged in said housingsymmetrically centered on an axis of said common input shaft so as toshare power from said common input shaft, wherein each of saidhydrostatic transmissions includes mutually fluidly connected hydraulicpump and motor, said hydraulic pumps being drivingly connected to saidcommon input shaft, and said hydraulic motors being drivingly connectedto said respective axles, and wherein said hydraulic pump and motor ineach of said hydrostatic transmissions have mutually perpendicularrotary axes.
 8. The axle driving apparatus as set forth in claim 7,further comprising: a PTO shaft disposed coaxially to said common inputshaft; and a clutch disposed in said housing and interposed between saidcommon input shaft and said PTO shaft.
 9. The axle driving apparatus asset forth in claim 8, further comprising: a brake which is appliedsimultaneously to disengagement of said clutch so as to prevent inertialrotation of said PTO shaft.